Production method for paper feed roller

ABSTRACT

A paper feed roller-producing method is to be provided, which enables more inexpensive mass produce of a high precision paper feed roller, with a high precision, having no connecting portion in a roller portion, by using a hydraulic composition. 
     The method for producing a paper feed roller includes a rotary shaft and a cylindrical roller portion integrated around an outer periphery of the rotary shaft, characterized in that the roller portion is formed by extruding a hydraulic composition and curing and hardening the extrudate.

TECHNICAL FIELD TO WHICH THE INVENTION BELONGS

The present invention relates to a method for producing paper feedrollers in which a hydraulic composition is used for roller portions andwhich are employed in apparatuses, such as printers, facsimile machinesand copying machines, requiring papers to be accurately conveyed.

PRIOR ART

Formerly, metallic rollers, rubber rollers, etc. have been used as paperfeed rollers. The metallic rollers have been each produced by attachingend plates with shaft portions to both end portions of a hollow metalliccylindrical body constituting a roller portion, respectively, bywelding. In this case, although a rotary shaft of the metallic roller isformed by the shaft portions at the opposite ends, there is a verydifficult problem in ensuring the concentricity between the metalliccylindrical body and the rotary shaft. Further, paper feed rollers inwhich a roller portion is constituted with hard rubber to reduce theweight have been used, but there is a problem in that errors are likelyto occur in feeding papers owing to large heat expansion of the rollerportion.

PROBLEMS TO BE SOLVED BY THE INVENTION

In order to solve the above-mentioned problems, Sumitomo Osaka CementCo., Ltd. made an invention directed to a method for the production ofan integrated paper feed roller by preparing a cylindrical molded bodyhaving a given length from a hydraulic composition according to a pressmolding method and fixing the molded body around the outer periphery ofa rotary shaft, and Sumitomo Osaka Cement Co., Ltd. filed an applicationtherefor under Japanese Patent Application No. 10-177,100. Further,Sumitomo Osaka Cement Co., Ltd. filed patent application under Japanesepatent application No. 11-28,137, etc. directed to a method for theproduction of paper feed rollers in which roller portions are formed byconnecting a plurality of cylindrical molded bodies.

According to this method, since the length of the cylindrical moldedbodies themselves can be shortened as compared with that of a desiredroller portion, non-uniform pressure applied during the press moldingcan be prevented, and a shaping mold can be made smaller. Further, ifthe length of a single cylindrical body is set based on the relationshipbetween the size of papers and the number of such cylindrical moldedbodies to be connected, and a plurality of the cylindrical molded bodieshaving a single shape are preliminarily prepared, plural kinds of paperfeed rollers can be easily produced depending upon the sizes of papersby using given numbers of the cylindrical molded bodies having a singleshape. This enables the inexpensive mass production of the paper feedrollers with a high precision.

However, since the roller portion is formed by connecting pluralcylindrical molded bodies in the above method, there is a problem inthat the hardness of the roller portion is low. Further, although therigidity can be increased by appropriately selecting an adhesive used inthe connecting portion, it leads to cost-up, and there is a limit forthe increase in the rigidity.

PROBLEMS TO BE SOLVED

The present invention is aimed at solving the above problems, andproviding a paper feed roller-producing method capable ofmass-producing, with a higher precision at a more inexpensive cost, ahigh-precision paper feed roller having no connecting portion at aroller portion according to an extrusion molding with use of a hydrauliccomposition.

The paper feed roller-producing method according to the presentinvention is a method for producing a paper feed roller comprising arotary shaft and a cylindrical roller portion integrated around theouter periphery of the rotary shaft, characterized in that the rollerportion is formed by extruding a hydraulic composition and curing andhardening the extrudate product.

The following will be recited as preferred embodiments of the paper feedroller-producing method according to the present invention.

(1) A hollow cylindrical molded body is extruded from the hydrauliccomposition, the rotary shaft is inserted through a hole of the moldedbody, and the molded body is cured and hardened to integrate the rotaryshaft and the roller portion.

(2) A hollow cylindrical molded body is extruded from the hydrauliccomposition, the molded body is cured and hardened, and the rotary shaftis inserted through a hole of the molded body to integrate the rotaryshaft and the roller portion.

(3) A hydraulic composition is concentrically extruded around the rotaryshaft, and cured and hardened to integrate the rotary shaft and theroller portion.

Among the above, the method (3) is most preferable.

The hydraulic composition preferably comprises 100 wt. parts of a mixedpowder, 2 to 9 wt. parts of a workability improver, and 0.5 to 5 wt.parts of a thickening agent, said mixed powder comprising 40 to 80 wt %of a hydraulic powder, 10 to 50 wt % of a non-hydraulic powder havingthe average particle diameter smaller than that of the hydraulic powderby an order of one digit or more, and 10 to 30 wt % of an extrusionimprover

The extrusion improver is preferably an inorganic scaly material. As theinorganic scaly material, talc and mica may be recited.

The workability improver is preferably a powder or emulsion composed ofat least one resin selected from a vinyl acetate resin or a copolymerresin with vinyl acetate, an acrylic resin or an acrylic copolymerresin, a styrene resin or a copolymer resin with styrene and an epoxyresin

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(a) is an illustrative view showing a step for extruding acylindrical molded body according to one embodiment of the paper feedroller-producing method according to the present invention,

FIG. 1(b) being an illustrative view showing a step for inserting arotary shaft through the thus obtained cylindrical molded body before orafter being cured and hardened, and

FIG. 1(c) being a front view showing the thus obtained paper feedroller; and

FIGS. 2(a) and 2(b) show an extruding apparatus directed to anotherembodiment of the paper feed roller-producing method according to thepresent invention.

In the following, the present invention will be explained in moredetail.

(1-1) Rotary Shaft

As the rotary shaft used in the present invention, those similar to theconventional rotary shafts in the paper feed rollers may be used. As tothe shape of the shaft, a shaft for supporting the hollow cylindricalroller portion as a paper-feeding portion may be cut and finished toprovide a bearing-fitting portion, a driving force transmissionmechanism-fitting portion or the like. As a material of the rotaryshaft, an ordinary material such as a SUS free cutting steel may berecited. The surface of the rotary shaft may be electrolessly platedwith Ni—P.

(1-2) Hollow Cylindrical Roller Portion

The cylindrical roller portion in the present invention is produced byextruding a cylindrical molded body from a hydraulic composition, andcuring and hardening the extrudate. The cylindrical roller portion andthe rotary shaft may be integrated by any one of the above-mentionedmethods (1) to (3).

In this case, the precision (a deviation precision) of the thus obtainedcylindrical roller portion may be at a high level as it is. However, ifthe roller portion is subjected to centerless cutting or the like, thecircularity of the cylindrical roller portion can be enhanced and theconcentricity between the roller portion and the rotary shaft can beimproved. The paper feed roller with a high precision can be obtained byenhancing the circularity and the concentricity.

The thickness of the cylindrical roller portion is determined by theouter diameter of the rotary shaft used and that of the paper feedroller. A tolerance of the diameter of the cylindrical roller portion isset at a given numeral value in design, which is ordinarily set at aworking accuracy of a desired outer diameter of ±0.003 mm. The surfaceof the cylindrical roller portion itself may be finished coarsely bysand blasting or the like.

2. Hydraulic Composition

The hydraulic composition used in the present invention comprises amixed powder of a hydraulic powder, a non-hydraulic powder and anextrusion improver, a workability improver and a thickening agent. Thecomposition may include other additive if necessary, and further watercontained upon necessity.

This will be detailed below.

(2-1) Hydraulic Powder

The hydraulic powder used in the present invention means a powder to becured with water, for example, a calcium silicate compound powder, acalcium aluminate compound powder, a calcium fluoroaluminate compoundpowder, a calcium sulfaminate compound powder, a calcium aluminoferritecompound powder, a calcium phosphate compound powder, a hemihydrate oranhydrous gypsum powder, a self-hardening lime powder and a mixed powderof any two or more kinds of these powders may be recited. As a typicalexample, powder such as Portland cement may be recited.

As to the grain distribution of the hydraulic powder, the Blaine'sspecific surface area is preferably not less than 2500 cm²/g from thestandpoint of ensuring the hydraulic property regarding the strength ofthe molded body. The compounding amount of the hydraulic powder is 40 to80 wt %, more preferably 45 to 55 wt %, of the mixed powder of thehydraulic powder, the non-hydraulic powder and the extrusion improver.

If the compounding amount is less than 40 wt %, the strength and thefilling percentage decrease, whereas if it is more than 80 wt %, thefiling percentage in obtaining the molded body decreases. Both cases areundesirable, because the molded body cannot withstand the working stressduring mechanical working.

(2-2) Non-hydraulic Powder

The non-hydraulic powder means a powder which will not be cured evenupon contact between water and it alone. The non-hydraulic powderincludes powders which each form a reaction product between otherdissolved ingredient through dissolution of that therefrom in analkaline or acidic state or in a high pressure steam atmosphere. Astypical examples of the non-hydraulic powder, mention may be made ofcalcium hydroxide powder, gypsum dihydrate powder, calcium carbonatepowder, slag powder, fly ash powder, silica powder, clay powder andsilica fumed powder, for example. The average particle diameter of thenon-hydraulic powder is smaller than that of the hydraulic powder by anorder of one or more digits, preferably two or more digits. The lowerlimit of the fineness of the non-hydraulic powder is not particularlyset, so long as the effects of the present invention are not damaged.

The compounding amount of the non-hydraulic powder is set at preferably10 to 50 wt %, more preferably 20 to 30 wt % of the mixed powdercomprising the hydraulic powder, the non-hydraulic powder and theextrusion improver.

If the compounding amount is less than 10 wt %, the filling percentagedecreases, whereas if it is more than 50 wt %, the strength and thefilling percentage decrease. Both cases are undesirable, because theyadversely affect various physical properties after molding andhardening, for example, chipping during mechanical working anddimensional stability. In considering the mechanical workability, etc.,it is preferable to adjust the compounding amount of the non-hydraulicpowder so that the filling percentage may not become too low. Theaddition of the non-hydraulic powder can increase the filling percentageof the molded body during molding and decrease the void percentage ofthe resulting molded body.

(2-3) Extrusion Improver

The extrusion improver used in the present invention is a material whichimproves slippage between a mold frame and the molded body duringextrusion, reduces anisotropy in moldability and stabilizes the quality.

As the extrusion improver, use may be made of inorganic scaly materialssuch as talc (hydrous magnesium silicate) and mica, for example. Suchinorganic scaly materials have excellent orientability and impartslipping property upon the surface of the molded body, so that thequality of the molded body is stabilized.

The compounding amount of the extrusion improver is preferably 10 to 30wt %, more preferably 15 to 25 wt % of the mixed powder comprising thehydraulic powder, the non-hydraulic powder and the extrusion improver.

(2-4) Workability Improver

The workability improver means a material that improves moldability,mold-releasability, cutting/grinding workability and grinding accuracyof the molded body obtained from the hydraulic composition, particularlythe material that contributes to improvement in cutting/grindingworkability and grinding accuracy. That is, since the workabilityimprover functions as a molding aid during the press molding, thehydraulic composition added with the workability improver improves themoldability. Further, the workability improver reduces brittleness ofthe cement-based hydraulic body, so that the molded body is releasedfrom the mold during the releasing step without being damaged at all,resulting in improvement in workability. In general, the molded bodyobtained from the hydraulic composition as a generally brittle materialexhibits a cut state of a “crack-type mechanism” in cutting. In thiscase, problems occur that the material is broken or chipped (includingmicroscopical phenomena).

Since the hydraulic composition in the present invention contains theworkability improper, it is possible to prevent cracking and chipping ofthe above material to which toughness is imparted to exhibit themechanical workability in the molded body as a solid material. That is,the workability of the molded body obtained from the hydrauliccomposition which has been difficult to effect mechanical workings suchas cutting, grinding, etc. can be improved to the same level as that ofthe metallic materials with the workability improver. The molded bodycan be cut with the lather or the like and ground with a cylindricalgrinder or the like as in the same manner as in the metallic materials.The molded body can be finely worked within an order of μm relative to adesired dimension.

The compounding amount of the workability improver is set at 2 to 9parts by weight, preferably 3 to 4 parts by weight, relative to 100parts by weight of the mixed powder of the hydraulic powder, thenon-hydraulic powder and the extrusion improver. The compounding amountof less than 2 parts by weight is not preferable, because cuttabilitydegrades. If it is more than 9 parts by weight, both the grindingaccuracy and the dimensional stability after the grinding degrade,although excellent moldability is obtained. The grain size is generallythat discrete grains are in a diameter range of not more than 1 μm.

As the workability improver, use may be made of a powder or an emulsionof at least one kind of resins selected from a vinyl acetate resin, acopolymer resin with vinyl acetate, acrylic resin or a copolymer withacryl, a styrene resin or a copolymer with styrene, and an epoxy resin.As the above vinyl acetate copolymer resin, a vinyl acetate-acrylcopolymer resin, a vinyl acetate-beova copolymer resin, a vinylacetate-beova terpolymer resin, a vinyl acetate-maleate copolymer resin,a vinyl acetate-ethylene copolymer resin, a vinyl acetate-ethylene-vinylchloride copolymer resin, etc. may be recited. As the acrylic copolymerresin, an acryl-stryrene copolymer resin, an acryl-silicone copolymerresin, etc. may be recited. As the styrene copolymer resin, astyrene-butadiene copolymer resin may be recited.

(2-5) Thickening Agent

The thickening agent is a material that exhibits adhesion when dissolvedin water. This agent is an ingredient effective for enhancing thebonding forces among the particles of the hydraulic powder and thenon-hydraulic powder, maintain the shape of the molded body aftermolding, ensuring the water holding ability and forming a compacthardened body.

As the thickening agent used in the present invention, mention may bemade of methyl cellulose, hydroxyethyl cellulose, carboxymethylcellulose, etc.

The compound amount of the thickening agent is preferably 0.5 to 5 partsby weight, preferably 3 to 4 wt. parts relative to 100 parts by weightof the mixed powder of the hydraulic powder, the non-hydraulic powderand the extrusion improver.

(2-6) Other Additives

In addition to the above indispensable ingredients (2-1) to (2-3), themixture comprising the hydraulic composition in the present inventionmay contain an aggregate, such as silica sand, as a bulk filler, at sucha rate that the aggregate is 10 to 50 parts by weight, preferably 20 to30 parts by weight relative to 100 parts by weight of the mixed powderof the hydraulic powder, the non-hydraulic powder and the extrusionimprover. In order to further improve the moldability, a known ceramicmolding aid may be added at a rate of 1 to 10 parts by weight,preferably 3 to 6 parts by weight relative to 100 parts by weight of themixed powder. Further, in order to suppress the dimensional change dueto the shrinkage of the material during hardening, a water repellant todecrease absorption of water, such as silicone oil, may be added at arate of 0.5 to 5 parts by weight, preferably 1 to 2 parts by weightrelative to 100 parts by weight of the mixed powder.

In order to formulate a molding mixture by using the hydrauliccomposition, the molding mixture is obtained by mixing the hydrauliccomposition, other additive to be added if necessary, and water in anamount of not more than 30 parts by weight and preferably not more than25 parts by weight relative to 100 parts by weight of the mixture of thehydraulic powder, the non-hydraulic powder and the extrusion improver.Water is preferably as few as possible from the standpoint ofsuppressing shrinkage on drying.

The mixing method is not particularly limited. Preferably, a mixingmethod or a mixer is preferred, which can afford powerful shearingstress upon the mixture. Since the average particle diameter of thenon-hydraulic powder is smaller than that of the hydraulic powder by anorder of not less than one digit, a time required for mixing will bevery longer to obtain a uniform mixture unless the shearing mixer isused.

Further, in order to make the handling of the mixture better in molding,the mixture may be granulated to a size suitable for a shape to bemolded, following the mixing. The granulation may be effected by using aknown method such as rolling granulation, compression granulation,stirring granulation or the like.

3. Method for Producing the Paper Feed Rollers

(3-1) Formation of Cylindrical Molded Bodies

A cylindrical molded body having a given length and a given outerdiameter is molded from a given hydraulic composition.

A. A hollow cylindrical roller molded body having a hole in a centralportion through which a rotary shaft is to be passed is extruded from ahydraulic composition in (1) a case where the hollow cylindrical rollermolded body is extruded, the rotary shaft is inserted through the holeof the molded body thus obtained, and the molded body is cured andhardened to integrate the rotary shaft and the roller portion and (2) acase where the hydraulic composition is molded in a hollow cylindricalform, the molded body is cured and hardened, and the rotary shaft isthen inserted through the hole of the hardened body. For example,extrusion molding is effected by using an ordinary extruding machineshown in FIG. 1(a), for example, and a hollow cylindrical roller moldedbody is obtained by cutting the extruded body in a given length. In FIG.1(a), 1 denotes the extruding machine, 2 a molding material, 3 a hollowcylindrical extruded body, 4 a cutter for cutting the extruded body, andR a hollow cylindrical roller molded body.

In a case (3) where a hollow cylindrical roller molded body isconcentrically extruded around a rotary shaft from a hydrauliccomposition, and the molded body is cured and hardened to integrate arotary shaft and the roller portion, the hydraulic composition isextruded into the roller molded body concentrically around the rotaryshaft by using an extruding machine shown in FIGS. 2(a) and 2(b). InFIGS. 2(a) and 2(b), 1 denotes an extruding machine having a cross head5 fitted to a tip portion of an extruding outlet of the extrudingmachine. While the rotary shaft 7 is downwardly fed inside a cylindricalguide 6 for the rotary shaft extended vertically within the cross head,the extruding material is extruded integrally around the rotary shaftwhen the material comes out through a tip end of the cross head. Then,rotary shaft portions are exposed by cutting off the hydrauliccomposition at opposite end portions of the rotary shaft.

(3-2) Rotary Shaft

The rotary shaft of the paper feed roller in the present invention isinserted through and fixed in the hole, while aligned, which is formedin a central portion of the cylindrical roller portion such that thehole may be concentrically with the outer peripheral face of thecylindrical roller portion. The entire length of the rotary shaft, thelength of the inserted portion and that of outwardly exposed portions ofthe rotary shaft are appropriately determined. If the rotary shaft isattached to the hole of the cylindrical roller portion with an adhesiveor the like, the outer diameter of the rotary shaft is smaller than thatof the inner diameter of the hole of the cylindrical molded body byaround 10 to 50 μm, preferably 10 to 30 μm. If it is less than 10 μm, itis difficult to assemble the cylindrical molded body around the rotaryshaft, whereas if it is more than 50 μm, the concentricity (deviationfrom the concentricity) between the rotary shaft and the cylindricalmolded body becomes larger, resulting in poor precision of the roller.If it is less than 30 μm, the cylindrical molded body can be attached tothe rotary shaft due to shrinkage following the hardening of thecylindrical molded body without using adhesive in combination.

(4) Assembling the Cylindrical Molded Body Around the Rotary Shaft

(4-1) First Method

A method for producing the paper feed roller according to the presentinvention comprises extruding a cylindrical molded body from a hydrauliccomposition, and thus obtaining the cylindrical molded body. A rotaryshaft 7 is inserted through a hole R′ in the center of the cylindricalmolded body R. In this case, the cylindrical molded body is formed suchthat it has strength high enough to be not broken during the insertionof the rotary shaft into the central portion of the cylindrical moldedbody. Thereafter, the cylindrical molded body is formed by curing andhardening, and the cylindrical roller portion is integrally formedaround the outer periphery of the rotary shaft.

(4-2) Second Method

A cylindrical molded body is extruded from the hydraulic composition, ahollow cylindrical roller portion is formed by curing and hardening, andthen a rotary shaft is inserted through and integrally fixed with a holeof the cylindrical roller portion.

(4-3) Third Method

A hollow cylindrical roller molded body is extruded concentricallyaround a rotary shaft from the hydraulic composition, and cured andhardened to integrate the rotary shaft and the roller portion.

The cylindrical molded body extruded may be cured and hardened by one orany combination of ordinary temperature curing, steam curing, autoclavecuring, etc. Considering the mass production, chemical stability of theproducts, dimensional stability, etc., autoclave curing is preferred.The hardening reaction of the cylindrical molded body can be completelyterminated by the autoclave curing for around 5 to 10 hours, so that adimensional change thereafter is extremely small.

In the above method, at least 10 μm clearance is necessary for fittingthe cylindrical molded body around the rotary shaft after curing andhardening. Since the cylindrical molded body does not shrink after thecuring with the autoclave, the cylindrical molded body may be fitted tothe rotary shaft with the adhesive or through forming a fittingclearance by cooling the rotary shaft or heating the cylindrical moldedbody. Alternatively, the rotary shaft may be press fitted into the holeof the cylindrical molded body. As the adhesive, an epoxy-basedadhesive, an urethane-based adhesive, an emulsion-based adhesive, asynthetic rubber-based adhesive, an acrylate-based adhesive or the likeis used.

In the second method, since the cylindrical molded body dimensionallyshrinks by 0.08 to 0.15% (depending upon the compounding condition)through curing with the autoclave, the inner diameter portion of thecylindrical molded body is formed, taking the shrinkage amount intoconsideration.

(4) Curing, Hardening

Since it takes a few hours to several days for the molded body toexhibit strength sufficient for mold-releasing after press molding,curing is necessary. The molded body may be left at room temperature asit is or cured in water or cured with steam. Curing in the autoclave ispreferred. If water is lacking or insufficient for forming the hardenedbody, steam curing is preferred. Particularly, curing in the autoclaveis preferred. The autoclave curing is effected at 165° C. or higherunder a saturated steam pressure of 7.15 kg/cm², preferably a saturatedsteam pressure of 9.10 kg/cm² or higher. The curing time depends uponthe curing temperature, and is 5 to 15 hours at 175° C. After the pressmolding, the molded body preferably exhibits compression strength ofaround 5 N/mm² before starting the autoclave curing. If the molded bodydoes not exhibit sufficient strength before the autoclave curing, themolded body will be cracked.

FIG. 2 is a sectional view of the extruding.

Best Mode of Embodiments EXAMPLES

Examples of the present invention will be explained below.

Example 1

A hydraulic composition was extruded by the method shown in FIG. 1, andcut in a given length, thereby obtaining a cylindrical roller moldedbody having a hole in a central portion thereof. After a rotary shaftwas inserted through the hole, a paper feed roller was produced bycuring and hardening the molded in the autoclave curing and thusintegrally fixing the roller portion around the outer periphery of therotary shaft. At that time, the paper feed roller portion shrunk byabout 0.2%, and fixed around the outer periphery of the rotary shaft.The materials used and dimensions were as follows.

Formulation in Example

The hydraulic composition had the following formulation, and was mixedby a kneader.

Mixed powder: 100 wt. parts

(Hydraulic powder: Portland cement 80 wt %)

(Non-hydraulic powder: silica fume 10 wt %)

(Extrusion improver: talc 10 wt %)

Workability improver: acrylic resin 5 wt. parts (based on dried weight)

Thickening agent: carboxylmethyl cellulose 2 wt. parts

Water: 25 wt. parts

Rotary shaft: SUM 22 L, outer diameter 8 mm, length 535 mm

Roller portion: outer diameter 22 mm, length 485 mm

After the roller portion was fixed around the outer periphery of therotary shaft, a paper feed roller with a high precision was produced byfinishing through centerless grinding.

Example 2

A hydraulic composition was extruded by the method shown in FIG. 1, andcut in a given length, thereby obtaining a cylindrical roller moldedbody having a hole in a central portion thereof. After a cylindricalroller portion was formed by subjecting the molded body to reactionhardening in autoclave curing, and a rotary shaft was inserted through ahole of the roller portion. Then, a paper feed roller was produced byintegrating and fixing the roller portion around the outer periphery ofthe rotary shaft with an adhesive. A clearance between the hole of thehardened cylindrical roller portion and the outer periphery of therotary shaft was around 20 μm. The materials used and dimensions werealmost the same as in Example 1.

Formulation in Example

The hydraulic composition had the following formulation, and was mixedby a kneader.

Mixed powder: 100 wt. parts

(Hydraulic powder: Portland cement 80 wt %)

(Non-hydraulic powder: silica fume 10 wt %)

(Extrusion improver: talc 10 wt %)

Workability improver: acrylic resin 5 wt. parts (based on dried weight)

Thickening agent: carboxylmethyl cellulose 2 wt. parts

Water: 25 wt. parts

Rotary shaft: SUM 22 L, outer diameter 8 mm, length 535 mm

Roller portion: outer diameter 22 mm, length 485 mm

Kind of adhesive: epoxy resin adhesive

After the roller portion was fixed around the outer periphery of therotary shaft, a paper feed roller with a high precision was produced byfinishing through centerless grinding.

Example 3

A hydraulic composition was extruded around the outer periphery of arotary shaft by using the method shown in FIG. 2, and a cylindricalroller molded body, which had a given length and a hole in a centralportion thereof, was integrally formed around the outer periphery of therotary shaft by cutting opposite end portions of the extruded body. Theroller portion was formed by reaction hardening in the autoclave curing.Materials used and dimensions were almost the same as those in Example1.

Formulation in Example

The hydraulic composition had the following formulation, and was mixedby a kneader.

Mixed powder: 100 wt. parts

(Hydraulic powder: Portland cement 80 wt %)

(Non-hydraulic powder: silica fume 10 wt %)

(Extrusion improver: talc 10 wt %)

Workability improver: acrylic resin 5 wt. parts (based on dried weight)

Thickening agent: carboxylmethyl cellulose 2 wt. parts

Water: 25 wt. parts

Rotary shaft: SUM 22 L, outer diameter 8 mm, length 535 mm

Roller portion: outer diameter 22 mm, length 485 mm

After the roller portion was fixed around the outer periphery of therotary shaft, a paper feed roller with a high precision was produced byfinishing through centerless grinding.

Comparative Example 1

Nine cylindrical roller molded body units each having a hole in acentral portion were formed by press molding a hydraulic composition byusing the method shown in FIG. 1, a rotary shaft was inserted throughthe holes of the molded body units, and the units were connectedtogether. Then, a paper feed roller was produced by curing and hardeningthe molded body units in the autoclave curing and thus integrating andfixing the roller portion around the outer periphery of the rotaryshaft. The paper feed roller portion was fixed around the outerperiphery of the rotary shaft through being shrunk by about 0.2%.Materials used and dimensions were the same as those in Example 1 exceptthat the length of the molded body unit was 54 mm.

Formulation in Comparative Example

The hydraulic composition had the following formulation, and was mixedby a Henschel mixer.

Mixed powder: 100 wt. parts

(Hydraulic powder: Portland cement 70 wt %)

(Non-hydraulic powder: silica fume 30 wt %)

Workability improver: acrylic resin 9 wt. parts (based on dried weight)

Water: 25 wt. parts

Rotary shaft: SUM 22 L, outer diameter 8 mm, length 535 mm

Roller molded body unit: outer diameter 22 mm, length 54 mm

Roller portion: length 486 mm

After the roller portion was fixed around the outer periphery of therotary shaft, a paper feed roller with a high precision was produced byfinishing through centerless grinding.

Comparative Example 2

Nine cylindrical roller molded body units each having a hole in acentral portion were formed by press molding a hydraulic composition byusing the method shown in FIG. 1, roller portion units were formed byreaction hardening the molded body units in the autoclave curing. Arotary shaft was inserted through the holes of the roller portion units,and a paper feed roller was produced by integrating and fixing theroller portion around the outer periphery of the rotary shaft with anadhesive. A clearance was about 20 μm between the hole of the hardenedroller portion and the outer periphery of the rotary shaft. Materialsused and dimensions were the same as those in Example 1 except that thelength of the molded body unit was 54 mm.

Formulation in Comparative Example

The hydraulic composition had the following formulation, and was mixedby a Henschel mixer.

Mixed powder: 100 wt. parts

(Hydraulic powder: Portland cement 70 wt %)

(Non-hydraulic powder: silica fume 30 wt %)

Workability improver: acrylic resin 9 wt. parts (based on dried weight)

Water: 25 wt. parts

Rotary shaft: SUM 22 L, outer diameter 8 mm, length 535 mm

Roller molded body unit: outer diameter 22 mm, length 54 mm

Roller portion: length 486 mm

After the roller portion was fixed around the outer periphery of therotary shaft, a paper feed roller with a high precision was produced byfinishing through centerless grinding.

With respect to the paper feed rollers obtained in Examples 1 and 2 andComparative Examples 1 and 2, a warped amount (mm) in a central portionof the roller was measured under the condition that two supportingpoints were spaced by a span of 300 mm and a 20 Kg load was applied to acentral portion of the roller between the support points. Results areshown in Table 1.

Warped amount (mm) Example 1 0.28 Example 2 0.31 Example 3 0.30Comparative Example 1 1.30 Comparative Example 2 0.62

As understood from the above results, the paper feed rollers in Examples1 to 3 according to the present invention in which the extruded rollerportion is integrated and fixed around the outer periphery of the rotaryshaft exhibited had smaller warped amounts and thus higher rigidity. Onthe other hand, it is seen that the paper feed rollers in ComparativeExamples 1 and 2 in which the roller portion is formed in a dividedmanner and integrated and fixed around the outer periphery of the rotaryshaft, while being connected together had larger warped amounts and thussmaller rigidity.

Industrial Applicability

According to the paper feed roller-producing method according to thepresent invention, the paper feed roller having high rigidity with noconnecting portion in the roller portion can be mass produced lessinexpensively with a high precision by extruding the hydrauliccomposition used.

What is claimed is:
 1. A method for producing a paper feed rollercomprising a rotary shaft and a cylindrical roller portion integratedaround an outer periphery of the rotary shaft, comprising the steps of:providing a rotary shaft; forming a roller portion by extruding ahydraulic composition along a rotational axis of the rotary shaft; andcuring and hardening the extrudate.
 2. The paper feed roller-producingmethod set forth in claim 1, wherein the hydraulic composition isconcentrically extruded around the rotary shaft, and cured and hardenedto integrate the rotary shaft and the roller portion.
 3. The paper feedroller-producing method set forth in claim 1, wherein the hydrauliccomposition comprises 100 wt. parts of a mixed powder, 2 to 9 wt. partsof a workability improver, and 0.5 to 5 wt. parts of a thickening agent,said mixed powder comprising 40 to 80 wt % of a hydraulic powder, 10 to50 wt % of a non-hydraulic powder having the average particle diametersmaller than that of the hydraulic powder by an order of one digit ormore, and 10 to 30 wt % of an extrusion improver.
 4. The paper feedroller-producing method set forth in claim 3, wherein the extrusionimprover is an inorganic scaly material.
 5. The paper feedroller-producing method set forth in claim 3, wherein the workabilityimprover is a powder or emulsion composed of at least one resin selectedfrom a vinyl acetate resin, a copolymer resin with vinyl acetate, anacrylic resin, an acrylic copolymer resin, a styrene resin, a copolymerresin with styrene and an epoxy resin.
 6. The paper feedroller-producing method set forth in claim 4, wherein the workabilityimprover is a powder or emulsion composed of at least one resin selectedfrom a vinyl acetate resin, a copolymer resin with vinyl acetate, anacrylic resin, an acrylic copolymer resin, a styrene resin, a copolymerresin with styrene and an epoxy resin.
 7. The method of claim 1, whereina tolerance of an outer diameter of the paper feed roller is suitablefor feeding paper.
 8. The method of claim 7, wherein the tolerance ofthe outer diameter of the paper feed roller is suitable for feedingpaper within one of a printer, facsimile machine, and a copy machine. 9.The method of claim 8, wherein the tolerance of the outer diameter ofthe paper feed roller is suitable for feeding paper within a printer.10. The method of claim 8, wherein the tolerance of the outer diameterof the paper feed roller is suitable for feeding paper within afacsimile machine.
 11. The method of claim 8, wherein the tolerance ofthe outer diameter of the paper feed roller is suitable for feedingpaper within a copy machine.